1. Field of the Invention
The present invention relates to systems and methods for shutting down an internal combustion engine coupled to a microprocessor controlled transmission to reduce or eliminate engine run-on.
2. Background Art
Engine run-on is a condition in an internal combustion engine where one or more combustion events occur in one or more engine cylinders after the ignition or key switch is turned to an off or shutdown position and the injector fuel flow is shut off. This condition may occur under certain operating conditions when a combustible mixture enters or remains in the intake or in one or more engine cylinders after the fuel injectors are shut off. While fuel may be supplied by various sources depending on the particular engine technology and design implementation, one source of such a combustible mixture may be the fuel and/or oil provided to the intake by a positive crankcase ventilation (PCV) system, for example.
Previous automated solutions to reduce engine run-on have included reducing inlet airflow by closing the throttle and idle bypass valves (for throttled engine applications), or engaging the torque converter clutch or lock-up clutch of an automatic transmission so the torque provided by the engine is not sufficient to maintain the run-on condition as disclosed in Japanese Pat. No. JP 9026027, for example. Similarly, the vehicle operator can place (or keep) the transmission in a driving gear while turning off the ignition switch so that the load imposed upon the engine by the transmission counters the torque provided by the engine in the run-on mode to stop the engine.